The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form off-line start-up circuits that received a voltage and formed an output voltage that was used for operating other circuits connected to the start-up circuit. In most cases, the start-up circuit formed a current that was used to charge a capacitor to generate the output voltage. In most cases, the current generated by the start-up circuit could vary if the value of the output voltage changed. Also, the current could change if the ambient temperature changed. As a result, it took much longer to generate the output voltage at high temperatures and than it did at low temperatures. This extra time period made it difficult to design circuits that utilized the output voltage. Additionally, the maximum value of the current typically was two to three (2-3) times the minimum value of the current thereby increasing the difficulty of using the prior off-line start-out circuits.
Accordingly, is desirable to have a start-up circuit that has a current that is stable over a range of temperatures, and that is stable as the value of the output voltage varies.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay between the reaction that is initiated by the initial action.